The present invention is directed to a process and apparatus for preparing an electrolyte bath and for replenishing an electrolyte in an electrochemical bath. More particularly, the invention is directed to a process for feeding a metal salt into an electrolyte solution that has been depleted of an electrolyte during an electrochemical process to replenish the solution with the electrolyte.
In recent years, there has been an increase in demand for corrosion resistant steel and processes of treating steel to impart corrosion resistance. High speed electroplating methods typically use high current densities. This type of electroplating method requires a rapid system for supplying the consumed electrolyte. Generally, this method uses an insoluble electrode and feeds the electrolyte into the bath in a soluble form.
An acid, such as sulfuric acid, is often used in electroplating zinc baths. The zinc is usually supplied as zinc oxide that is dissolved or dispersed in water and then dissolved in the sulfuric acid. Metallic zinc can be added to the acid bath which will dissolve in the sulfuric acid. Zinc in metal form is generally less preferred since the metallic zinc dissolves slowly in sulfuric acid and is not suitable for high production plating devices.
Conventional electroplating plants usually include a mixing tank, separate from the treating bath, for dissolving the metal source in the plating bath. The mixing tanks typically include an agitator and a steam connection for dissolving the metal source. The metal source is usually added in the form of a metal salt. The metal salts are dissolved in hot water and then transferred to the tank for the treating bath. Some metal compounds, such as zinc oxide, cannot be added directly to the acid bath and must first be dissolved in hot water.
The metal salts and metal compounds are often toxic and product large quantities of dust when added to the mixing tank. The metal salts are usually supplied in containers such as barrels or bags which expose the workers to large amounts of toxic dust, thereby increasing the health risks to the workers.
Modern electroplating plants using insoluble anodes require continuous resupplying of the metals being deposited on the substrate. The metals must be supplied to the plating bath either by dissolving the metal directly or by the addition of galvanic salts. In a similar manner, conducting salts also must be added continuously to the electrolyte bath to increase the conductivity of the electrolyte bath and reduce the electrical power consumption. The conducting salts are continuously depleted during the plating process with the primary plating metal and must be replenished.
High output plants typically use a silo and an automatic weighing device to supply the salts to the bath. The plants also include a dosing device to feed the salts to the dissolving tank. The tanks require expensive dust recovery devices to prevent the escape of dust particles to the atmosphere. The handling of the toxic dust particles complicates the operations and operating costs.
The prior large scale plants and the feeding and mixing arrangements form lumps in electrolyte bath when the salts are added. The agitating devices in the mixing tanks are not always able to prevent the formation of lumps in the bath.
Accordingly, there is a continuing need in the industry for improved systems for electrochemical treatment plants.
The present invention is directed to a process and apparatus for preparing an electrolyte solution and replenishing an electrolyte in an electrochemical treatment bath. More particularly, the invention is directed to a process and apparatus for supplying a metal salt to an electroplating bath.
Accordingly, a primary object of the invention is to provide a method and apparatus for feeding a metal salt to an electrolyte bath to replace the metal ion and other salts consumed in an electroplating process.
A further object of the invention is to provide a process and apparatus for adding electrolyte salts and/or chemicals to the electrolyte bath by the vacuum generated in a powder wetting machine.
Another object of the invention is to provide a process and apparatus for adding electrolyte salts and/or chemicals to an electrolyte bath from one or more tanks, silos or containers via one or more weighing devices to calculate the precise amount of galvanic salts and/or chemicals required to be added, where the calculated amount corresponds to the amount of electrolyte consumed in an electrochemical treatment process.
A further object of the invention is to provide a process and apparatus for adding the galvanic salts and/or chemicals continuously to an electrolyte bath. The galvanic salts and/or chemicals can also be added periodically in cycles according to the rate of consumption of the metal ions from the electrolyte solution.
Another object of the invention is to provide a process and apparatus having a reaction tank downstream of a powder wetting machine to provide a reaction time between 1 and 60 minutes, preferably between 1 and 10 minutes, prior to supplying to a reaction tank to replenish an electrolyte bath with a galvanic salt.
A further object of the invention is to provide a pump for directing an electrolytic liquid to a powder wetting machine.
Still another object of the invention is to provide a process and apparatus using a pump for directing an electrolytic liquid back to an electrolytic tank from a reaction tank.
Another object of the invention is to provide a process and apparatus for determining electrolyte consumption from an electrolyte bath by obtaining pH measurements, turbidity measurements, photometric or conductivity measurements or of an analysis of the dissolved ions by means of X-ray fluorescence of an electrolyte bath, and regulating the input feed of galvanic salts and/or chemicals to a powder wetting machine for replenishing the bath with an electrolyte.
A further object of the invention is to provide a method and apparatus for replenishing the consumed galvanic salts and/or chemicals in proportion to the surface area of a substrate being treated with an electrolyte bath. The galvanic salts and/or chemicals consumed can also be replenished in proportion to the depositing electric current in an electroplating plant.
The objects of the invention are basically obtained by providing a process of supplying a soluble metal compound to an electrolyte solution comprising providing an electrolyte solution and directing the electrolyte solution through a powder wetting device and producing a vacuum in the powder wetting device, and supplying a soluble metal compound to the vacuum to draw the soluble metal compound into the device and dispersing the soluble metal compound in the electrolyte solution passing through the powder wetting device.
The objects of the invention are further attained by providing a process for electrochemically treating a metal substrate comprising the steps of: supplying an electrolyte solution to an electrolytic tank, contacting a metal substrate with the electrolyte solution in the electrolytic tank, applying an electric current through the electrolyte solution to treat the metal substrate, continuously directing the electrolyte solution from the electrolytic tank to a powder wetting device and producing a vacuum zone in the powder wetting device, supplying a soluble metal compound to the vacuum zone in the powder wetting device and drawing the metal compound into the powder wetting device and dispersing the compound in the electrolyte solution, and returning the electrolyte solution to the electrolytic tank.
The objects of the invention are further attained by providing an apparatus for treating a metal substrate with an electrolyte solution. The apparatus comprises a treating tank for containing an electrolyte solution and for treating the metal substrate, a powder wetting device connected to the treating tank for receiving the electrolyte solution and forming a vacuum zone in the powder wetting device, a conduit for directing the electrolyte solution from the powder wetting machine to the treating tank, and a supply for supplying a soluble metal compound to the vacuum zone in the powder wetting machine for dispersing the metal compound in the electrolyte solution.
The objects, advantages and other salient features of the invention will become apparent to one skilled in the art as described in the following detailed description of the invention and the annexed drawings.